Establishment of high-resolution Cretaceous chronostratigraphy and tephrochronology in Japan

2015 Fiscal Year Final Research Report

• Project/Area Number: 25287130
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Tohoku University
• Principal Investigator: Takashima Reishi 東北大学, 学術資源研究公開センター, 准教授 (00374207)
• Co-Investigator(Kenkyū-buntansha): NISHI Hiroshi 東北大学, 学術資源研究公開センター, 教授 (20192685) ; YAMANAKA Toshiro 岡山大学, 自然科学研究科, 准教授 (60343331) ; ORIHASHI Yuji 東京大学, 地震研究所, 助教 (70313046) ; KURODA Jun-ichiro 国立研究開発法人海洋研究開発機構, 生物地球化学研究分野, 研究員 (10435836) ; MATSUBARA Takashi 北海道教育大学, 教育学部, 准教授 (30311484)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 白亜紀 / 地質年代 / 凝灰岩 / テフロクロノロジー

Outline of Final Research Achievements

In order to establish high-resolution international Cretaceous chronostratigraphic framework, we studied 206Pb/238U zircon geochronology of the 30 tuff beds that occur in the Yezo Group, Hokkaido, Japan. The 206Pb/238U ages of tuffs in the Yezo Group show that Aptian-Campanian interval ranges from 120 to 84 million years ago. Furthermore, we extracted apatite phenocrysts from the tuff beds, and analyzed trace element chemistry of the apatites. Based on the contents of magnesium and chlorine in the apatites of the tuffs in the Yezo Group, we found four tuff beds that are traceable throughout Hokkaido.

Free Research Field

地質学・層序学